1. Field of the Invention
This invention relates in general to data storage and processing, and more particularly to the management of an operator interface.
2. Description of Related Art
The implementation of new technology in magnetic tape products has meant that the density of data written to tape has increased by orders of magnitude in the last ten or fifteen years. The ability to record high density tapes, e.g., ten gigabytes or more on one physical volume, has led to reducing costs in physical tape hardware as well as in handling and management resources.
However, over the past five years, tape data set stacking products, i.e., software solutions to increase tape utilization, have evolved in response to the customer requirement for more efficient ways to manage the information stored on tape. Often a tape library system is provided in conjunction with a library manger. For example, a virtual tape server (VTS) having a tape library has been proposed to achieve increased capacity. In a VTS, the hardware is transparent to the host and the user. The VTS requires little external management except though the library management element of the tape library into which a VTS is integrated.
In a hierarchical storage systems, such as a VTS, intensively used and frequently accessed data is stored in fast but expensive memory. One example of a fast memory is a direct access storage device (DASD). In contrast, less frequently accessed data is stored in less expensive but slower memory. Examples of slower memory are tape drives and disk drive arrays. The goal of the hierarchy is to obtain moderately priced, high-capacity storage while maintaining high-speed access to the stored information.
In the VTS system, a host data interface, a DASD, and a number of tape devices are provided. When the host writes a logical volume, or a file, to the VTS, the data is stored as a file on the DASD. Although the DASD provides quick access to this data, it will eventually reach full capacity and a backup or secondary storage system will be needed. An IBM 3590 tape cartridge is one example of a tape device that could be used as a backup or secondary storage system.
When the DASD fills to a predetermined threshold, the logical volume data for a selected logical volume, typically the oldest, is removed from the DASD to free space for more logical volumes. The selected DASD file is then appended onto a tape cartridge, or a physical volume, with the original left on the DASD for possible cache hits. When a DASD file has been appended to a tape cartridge and the original remains on the DASD, the file is "premigrated".
When the host reads a logical volume from the VTS, a cache hit occurs if the logical volume currently resides on the DASD. If the logical volume is not on the DASD, the storage manager determines which of the physical tape volumes contains the logical volume. The corresponding physical volume is then mounted on one of the tape devices, and the data for the logical volume is transferred back to the DASD from the tape.
Tape servers may use an engine to move data between the DASD and tape libraries in a virtual tape server (VTS) environment. For example, the IBM Virtual Tape Server (VTS) uses the IBM Adstar Distributed Storage Manager (ADSM) as its engine to move data between the DASD and IBM 3590 tape drives on the VTS. In such a system, the VTS uses the a storage manager client on the DASD, e.g., the ADSM Hierarchical Storage Manager (HSM) client, and a distributed storage manager server attached to the tape drives to provide this function.
A tape library dataserver provides automated tape storage for multiple applications such as mid-range computer facilities, LAN servers and archiving applications. To provide high frequency to data, high storage capacity and high performance must be combined. Therefore, knowing the location of tape cartridges in the tape library is paramount. Typically, the tape cartridges are bar-coded with a serial number or other identifying marking. Thus, an accessor that is equipped with a bar-code reader can access any cartridge in the library. In addition, the accessor can mount any cartridge located in the library on any library drive. The accessor's management feature permits rapid scanning of all tape cartridge bar-codes.
Various functions and indicators are available to the operator of an automated tape library in order to facilitate library operations. These can include lights to indicate various library states or modes or convenience input/output station states on or near the operator panel.
Keeping these status lights and the states themselves synchronized with the actual state of the library is accomplished within the library manager controller, more specifically, the accessor manager controller. In a dual library manager/dual accessor environment, however, there are two accessor manager controllers, one of which is in control of the operator panel status. In the event of an accessor failure, the other accessor manger may take over the accessor operation including the state of the operator panel. However, by switching to the second accessor controller, the states of the library may not be maintained.
It can be seen that there is a need for a method and apparatus that allows control of the operator panel and convenience input/output station status lights by more than one accessor controller.
It can be seen that there is a need for a method and apparatus that allows a second accessor controller to maintain the states of the operator panel and convenience input/output station without reinitializing at a default condition.